Brake mechanism for motor vehicles



Oct. 20, 1931. w. J. BESLER 5 BRAKE MECHANISM FOR MOTOR VEHICLES Filed May 18. 1928 INVENTOR.

ATTORNEY.

Patented Oct. 20, 1931 I 7 UNITED STATES PATENT OFFICE WILLIAM J. IBESLER, OF PLAINFIELD; NEW JERSEY BRAKE mncnamsm ron MOTOR. VEHICLES Applicationfiled m 1a. 1928. Serial No. 278,721.

My invention relates to brake mechanism for motor vehicles and more particularly to brake mechanism of the fluid-pressure operated or servo-motor type, this application 5 being. a continuation in part of my copending application Ser'. No. 199,801, filed June 18, 1927, issued June-12, 1928, No. 1,673,177.

In the design of servo-motor brake mechanism, it is customary to provide a motor deavice which is suflicientl powerful to exert a greater braking effort than the minimum effort required tocontrol the vehicle. It is clear therefore that particulary where-such mechanism is designed for a large vehicle and is also used for asmaller vehicle, the motor is appreciably larger than necessary. The disadvantage of this result is that when the vehicle is operated by careless or lnexpert drivers, the brakes are frequently applied with excessive rapidity and force, resulting in rapid wear of the brakes and tires. Furthermore, the use of such mechanism is dangerous under some circumstances inasmuch 'as it is relativel diflicut to avoid dragging 2 the wheels w ich under some road con tions induces skidding.

Not only is it diflicult to select a servo-motor of the size which is properly proportioned to the weight of the vehicle and, its particularbraking system, but in actual operation this proportion is soon upset due to the variance in the amount of effort necessary to stop the car under varying conditions of the brake bands which may be new and '35 grip easily, or old and worn smooth,"or wet,

or covered with oil.

It is an object of my invention to provide simple and reliable means for adjusting the effectiveness of the power actuating mecha- 40 nism and more particularyto limit the power exerted thereby below that necessary to drag the wheels of the vehicle. I

A further object of my inventionis to provide a means whereby the driver can' dev crease or increase the strength of the servomotor to meet varying cond1t1ons of the braking system. Thus he can have a powerful force to apply when the brake bands are not gripping well-and modifythis force so that application will not be too severe or liable to cause dragging of the wheels when the brake bands are holding well.

A relatively powerful motor device may be employed, the same size being used for different sizes of vehicles and the effectivenessofthe operating mechanism is controlled by the auxiliary controlling device.

In its broader aspect, the invention contemplates the correlating of the force that may be exerted by the brake motor to the size and braking equipment of the vehicle in order that it may be difiicult or impossible to dra the Wheels of the vehicle under ordinary consider it preferable to provide a brake mo raking conditions. However, I

tor of ample size and limit the operating force of the motor by means of an auxiliary controlling device as set forth above so that the mechanism may be further adjusted at will to the varying conditions of the braking system.

In accordance with a preferred embodiment of the invention, the auxiliary controlling device maycomprise a simple reducing valve in the fluid-pressure line between the intake manifold of the engine and the fluidpressure motor. The reducing valve, which may be adjustable, is effective to control the pressure of the fluid supplied to the motor, and accordingly servesto limit the power thereof to attain the desired results.

Other objects and advantages of my invention will appear from the following detailed description of the embodiments shown in the accompanying drawings.

Referring to the drawings, Fig. 1 is a plan view 'of brake mechanism embodying the invention as applied to an automotive vehicle; Fig. 2 is a similar view of-a modified form of the invention embodying an adjustable controlling device for the servo-motor;

Fig. 3 is a detail view of the control lever, a main control valve and auxiliary valve of the brake mechanism shown in Fig. 2; and

Fig. 4 is a detail sectional viewof the main control valve taken on the line IV IV of portion of the chassis of an automotive vehicle is shown conventionally in Fig. 1, and comprises a frame including longitudinal members 1 and 2 and cross members 3 and 4 mounted in any suitable manner upon front and rear wheels '5 and '6, respectlvely. For the purposes of illustration, the rear wheels 6 of the vehicle are shown as provided with friction brakes 10 of any usual type which are rendered operative by one or more power: actuating devices such as the fluid-pressure motor 11.

It will be understood that the form and h to be described in connection with the modification of Fig. 2, and the operation will be-.

come clear from the following description of this modified form of the invention.

The inventive concept involved in the modification of Fig.- 1 resides in the correlation of the size or power of'the servo-motor 11,

taking into consideration the normal available pressure of the operating fluid where a flui -pressure motor is employed, with" the characteristics of the friction brakes 10 and the weight of the vehicle equipped with the brakes in order to obtain the new and desirable result; namely, a limitation of the braking effort of the-servo-motor such that full energization thereof shall be ineffective to drag the wheels 6 of the vehicle under predetermined road conditions, preferably upon a dry, smooth dirt or concrete road surface. This result is therefore obtained by a suitable poportioning of the parts of the braking mechanism and must be arrived at by experimentation for different vehicles and different types and sizes of friction brake elements.

The braking effort of the servo-motor may be supplemented, if necessary, by manual pressure upon the lever 20 in the modification shown, so that as much efi'ort may be exerted as may be required under anyconditions. On the other hand, since the maximum deceleration of the vehicle is attained just before the wheels be 'n to slip on the pavement, the natural ten ency'of the operator or driver to rely on a full application of the servo-motor to effect a sudden stop results in a braking operation of maximum efliciency without the exercise of any particular skill. Furthermore, the limitation placed 'upon the power of the braking mechanism has the further advantage that during the ordinary operation of the vehicle b careless or unsln'lled drivers, accidental ragging of the wheels is substantially prevented, thereby obviating the resultant wear and derangement of the brakes and tires, and reducing the danger from the skidding sometimes caused thereby.

In order to compensate for the varym conditions of the road and the ph sica changes of the braking system broug t on by wear, grease or water on the linings, without changing the size of the servo-motor, a large motor may be used and an auxiliary con'trollin device employed to limit the effectiveness of the motor. In the case of a fluidpressure motor, a throttling or pressure-reducing valve, preferably adjustable from the driver s seat may be arranged in the line leading to the motor.

For example, as shown in Fig. 2, an auxiliary valve 25 may be connected in the pressure line between the intake manifold 15 and the motor 11. Thevalve 25 may be arranged in the pipe connection 18 in series with the main control valve 19.

The detailed construction of the main and auxiliary controlling valves may be similar to that shown in Flgs. 3 and 4. As shown herein for purposes of illustration the main 'control valve 19 comprises a cylindrical base "member 30 adapted to receive the brake rod brakes 10. However, the forward end of the brake rod 31 is provided with a slotted portion 33 to provide a predetermined amount of lostmotion in order that the initial movement of the brake pedal shall be effective to actuate the control valve 19 before the brake pedal engages the brake rod 31.

The control valve 19 further comprises a member 34 pivoted as indicated at 35 upon the base portion 30 and connected through a pin 36 and rod 37' to the brake pedal 20. The base member 30 of the valve 19 is provided with two spaoedport openings 40 and 41 (see Fig. 3), and the pivoted element 34 of the valve is provided with a cooperating port opening 42 adapted to register with the port openings 40 and 41 when the element 34 is turned upon the pivot 35 by the brake pedal.

The auxiliary valve 25 comprises a hollow body portion 45 containing valve member 46 and valve seat 47, the valve member 46 being preferably of the ball type. The body'portion 45 of the valve 25 is provided with suitable passages 48 and 49 adapted to be conineans of a spring 50 andan adjusting screw 51. In the embodiment .of the invention illustrated herein the source of fluid pressure for operating the servo-motor is the intake manifold of an engine in which the pressure is lower than atmospheric pressure.

The operation of the main control valve 19 serves to connect the servo-motor 11 to the intake manifold 15 to apply the brakes and to exhaust the same to atmosphere through the atmospheric port 41' to release-the brakes. Theoperation is effected by depressing and releasing the brake pedal 20. The depression of the brake pedal 20 serves to rock the valve member 34 in the counter-clockwise direction as shown in Fig. 3, thereby placing vthe ports 40 and 42in communication with each other. If the brake pedal 20 is only slightly depressed, the energization of the servo-motor 11 takes up the slack in the brake mechanism and moves the brake rod 31 forward, thereby causing such a relative move- 'ment of the-valve members 30 and 34 as to ing of the wheels of the vehicle under ordi-* nary road conditions. Upon the release of the brake pedal 20, the reverse movement of the valve member 34 with respect to the cooperating valve member 30 brings the ports 41 and 42 into registration and vents the servo-motor 11 to atmosphere, thereby 'releasing the brakes;

The valve 25 maintains a pressure difiervential, depending upon the adjustment of the valve spring 50, which is continuously subtracted from the effective pressure for operating the brake motor. The maximum vacuum or subatmospheric pressure forenergizing the motor is less than the maximum vacuum of the intake manifold by the amount of the pressure differential across the valve 25. In this manner the maximum suction available for energizing the-motor is regulated by the valve 25. In order to prevent locking the wheels of the vehicle when the brakes are applied, the valve 25 is ad usted by the adjusting screw 51 to limit the maximum suction efiective on the brake motor below the suction that would cause locking of the wheels of the vehicle. I

" It will be apparent that the brake mechanism described above possesses several important advantages, particularly with re spect to the ease of handling the vehlcle so that the full advantages of servo-motor tions, such as in dense trafiic, might cause brakes ma be utilized by careless or inexpert drivers. urthermore even in the handset practiced drivers, the limitation of the power of the brake motor serves to lessen the wear on the brakes and tires because of the correlation of the maximum braking efiort that may be exerted to the weight or size of the vehicle and effectiveness of the friction brakes.

It is of advantage to have the reducing valve controllable from the drivers seat, for example by an operating lever or button on the instrument panel 52, so that the brakes may be adjusted quickly and easily at will to suit the condition of the road or changes in the adhesionof the brake bands caused by wetting in rainy weather or othercauses. Experience has also shown that it is better to decidedl limit the force of the servo-motor before a lowing a driver who is not accustomed to servo-motor brakes to take control of the vehicle as he is liable unintentionally to stop too suddenly which under certain condi- 1 collision or accident. g g

It will be apparent to those skilled in the art that the brake mechanism shown and .described ma be variously modified without departing rom the scope of the invention as set forth in the appended claims.

I claim:

1. A braking system for vehicles compris-. ing a brake, a power-actuating device for the brake, means for controlling the power-actuating device to apply and release the brake and means for decreasing by a predetermined constant the effectiveness of said power actuating device.

2. A brakin system for vehicles comprising a brake, a uid-pressure motor for applying the brake, a pipe connection leading to sa1d motorand a pressure-reducing valve in said connection for decreasing the efi'ectivefluid-pressure motor'and a pressure-reducing valve in sa1d connection for decreasing by a constant the effectiveness of the motor and controllable from the'drivers seat.

5. In a braking system for vehicles embodying brakes j ointly controlled by a servomotor and by a control lever, the initial move-' ment of the control lever rendering the servomotor operative and the continued movement '4 mes es supplementing the operation thereof in accordance with the extent of movement of said lever, a source of fluid power for said servomotor, means for reducing by a predetermined constant the efiectiveness of said fluid power and means for regulating said reducing means. 6. In a braking system for wheeled vehicles, brakes for some of the wheels, a servomotor for operating said brakes, a source of fluid pressure differential for said motor, and regulatable means for reducing the eflectiveness of said pressure differential by a predetermined constant to prevent locking of the vehicle wheels.

WILLIAM J. BESLER. 

